1. Field of the Invention
The present invention pertains to a composite and process for the in-situ preparation of a composite comprising a cationic clay and binder/matrix material.
2. Description of the Prior Art
Examples of these types of crystalline clays include smectite clays. Smectite clays have several applications in the catalyst field and as absorbents. For most commercial applications crystalline clays are formed into shaped bodies such as spheres, micro-spheres and extrudates. In all these applications where shaped bodies are exposed to severe processing conditions and environments, such as oil refinery applications, separations, purifications, and absorption processes, it is of paramount importance that the integrity of the shaped bodies containing smectite clay is kept intact and attrition is prevented.
In the prior art, crystalline Mgxe2x80x94Alxe2x80x94Si-containing clay is usually incorporated as a physical mixture with binder or matrix material in order to obtain attrition resistant shaped bodies. Commonly used binder/matrix or matrix material is alumina prepared from alumina precursors such as aluminum chlorohydrol, soluble alumina salts, and acid dispersed pseudoboehmite, silica such as silica sols, silicates, silica-alumina cogels, and combinations thereof.
However, when smectite clay is embedded in a matrix, the amount of active crystalline clay ending up in the resulting shaped bodies is relatively small because of dilution of the clay by binder or matrix material. There are applications in which for performance reasons it is desired that the shaped bodies consist or mostly consist of active crystalline clay. Also, by the incorporation of smectite clay into matrix material, physical properties of the crystalline clay such as specific surface area, pore size distribution, etc. may be detrimentally affected. Further, the distribution of the crystalline clay within the matrix is difficult to control, and usually large size aggregates of the individual components exist and prevent the formation of fine homogeneous dispersions. Another disadvantage of having to use a binder/matrix to obtain attrition resistant bodies is the fact that most commonly used binder/matrix materials have some chemical activity, which in certain applications can cause undesirable side reactions. For instance, the one of the most commonly used binder material in FCC catalysts and additives is silica or silica based material. These types of binders are not suitable for use in sulfur oxides removal additives, because they detrimentally affect the sulfur removal.
In one embodiment, the present invention is directed to a process for the in-situ preparation of a composite comprising a cationic clay and binder/matrix material from sources comprising an aluminum containing source, a silicon containing source and a di-valent metal containing source comprising the steps of:
a) preparing a precursor mixture by mixing the aluminum containing source, the silicon containing source and the di-valent metal containing source with seeding material,
b) homogenizing the precursor mixture, and
c) aging the precursor mixture to obtain the composite.
One or two of the aluminum containing source, silicon containing source or di-valent metal containing source is to be in excess of the amount required for stoichiometry of the three sources with respect to the formation of the cationic clay. The excess source or sources will form the binder/matrix material of the composite.
In a second embodiment, the present invention comprises a body comprising a crystalline clay comprising divalent metal-Alxe2x80x94Si wherein any binding material is present in a discontinuous phase.
Other embodiments of our invention encompass details about compositions, manufacturing steps, etc., all of which are hereinafter disclosed in the following discussion of each of the facets of the present invention.